If the GOP gets 51 on Election Day, they could end up with 53, either effectively, or in actuality.
Lieberman might retire or he might realize that he can't win a Democratic Primary and take his chances. Or, at 70, he may retire.
I could see Lieberman switching Republican then retiring, with hopes on a Republican administration in 2013 and a cabinet appointment. Nelson will stay in the Democratic party because he's not hated there and has a better chance getting a post-Senate job there than in the Republican party.
